reactionary

1. (politics) Extremely conservative; opposing revolution (such as the French Revolution); favoring a return to a golden age of the past.Examples: "There's a fairly simple reason for the embrace of radicalism on the right, and it has to do with the reactionary imperative that lies at the core of conservative doctrine. […] If he is to preserve what he values, the conservative must declare war against the culture as it is."; "[Jeffrey] Epstein was interested in transhumanism, a theory of human perfection via technological manipulation that—like its predecessor, eugenics—is shot through with racist and reactionary ideas."Synonyms: antiprogressive, regressiveAntonyms: progressive, nonreactionary

2. (chemistry) Of, pertaining to, participating in, or inducing a chemical reaction.Examples: "Psychiatry extends the theory into biology in the belief that all human behavior is nothing more than a series of reactionary chemical processes in the brain that determine pre-coded genetic responses built up from the conditioning of one’s environment."